Marine Engine Exhaust Silencing System

ABSTRACT

A silencing system for a marine exhaust system incorporates a single muffler for each engine of the marine vessel. The muffler is provided with two sound dampening chambers interconnected by several exhaust openings between the chambers. A Y-shaped exhaust type system directs exhaust streams from both sides of an engine toward a single exhaust conduit which extends through a transom of the marine vessel. The muffler is provided with a drain opening that allows water to flow out of the first chamber of the muffler in order to maximize the available volume within that chamber for use in sound attenuation. The outlet of the second chamber is provided with a baffle plate that directs the flow of exhaust gas in a forward direction toward the transom of the marine vessel and a deflection surface that directs the exhaust gas to flow in a downward direction toward the surface of the body of water in which the marine vessel is operated.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention is generally related to a marine exhaust system and, more particularly, to a silencing system for use in reducing noise emanations from the marine exhaust system.

2. Description of the Related Art

Many different types of muffler systems are well known to those skilled in the art of marine engines and exhaust systems.

U.S. Pat. No. 4,100,994, which issued to Stuart on Jul. 18, 1978, describes a marine exhaust silencer. It quiets the exhaust output from a marine engine by injecting a spray of cooling water into the exhaust passageway to mix with and cool the exhaust gases before output from the passageway. The exhaust passageway preferably enlarges substantially in cross-sectional area in the region where the mixing occurs between the injected water and the exhaust gases for enhancing the cooling effect. An inlet scoop receives water as the boat moves forward and the water is forced through a line and into the exhaust passageway in a way that breaks the water into droplets for contacting and cooling the exhaust gases. A mute that is preferably conical in shape and centered in the exhaust outlet also cooperates to reduce the exhaust noise.

U.S. Pat. No. 4,184,566, which issued to Baker et al. on Jan. 22, 1980, describes a marine engine noise suppressor. It is adapted for marine use wherein water coolant is discharged into the chamber of a singled walled riser and partially vaporized by the exhaust gases directed into the dome thereof for downward redirection and discharge from the lower portion of the riser chamber through a muffler element and preferably through a hull chest and/or cover of a jet pump drive acting as the final noise barrier to atmosphere.

U.S. Pat. No. 4,781,021, which issued to Winberg on Nov. 1, 1988, discloses a marine engine exhaust muffler assembly. It includes inlet and s outlet members, the axes of which are offset from each other. A muffler housing is disposed between the inlet and outlet members and forms a chamber having disposed therein an annular multi-layered cartridge, and with the layers having the multiplicity of perforations therein for passage of exhaust gases and spent engine cooling water thereof. The water assists in keeping the muffler clean. An imperforate arcuate blocking plate is nested within the lower portion of the cartridge to permit accumulation of the spent engine cooling water within the cartridge to aid in noise reduction at certain engine speeds. The blocking plate is provided with a relief opening means for assisting in water drainage upon engine shutoff.

U.S. Pat. No. 4,786,265, which issued to Porter on Nov. 22, 1988, describes a marine engine exhaust muffler. The muffler is mounted on the transom of an inboard or inboard/outboard motor boat around the exhaust pipes which extend from the transom. It comprises a housing which has a pair of side walls each adjacent to one of the sides of the boat, so that the housing is approximately equal in width with the width of the boat at the stem. Inside the housing is a baffle extending downwardly from the top of the housing which directs the exhaust downwardly around the bottom of the baffle to reduce the noise emanating from the exhaust.

U.S. Pat. No. 5,048,291, which issued to Rodskier on Sep. 17, 1991, describes an exhaust muffler for marine engines with two rows of cylinders. The muffler comprises a horizontal cylindrical container mounted transverse to the rows of cylinders and having an exhaust inlet and an exhaust outlet for reach row of cylinders. The container is mounted between the rear of the engine and the boat transom.

U.S. Pat No. 5,329,074, which issued to Alexander on Jul. 12, 1994, describes a marine engine exhaust muffler. It is mounted on the transom of a power boat in association with the exhaust pipes which extend through the transom. The muffler comprises a housing extending laterally across the stem of the boat and rearwardly from the transom to define an interior space. The housing has a floor located below the water line, opposed end walls, a front wall located adjacent to the transom with openings formed therein, through which exhaust gas can pass from the exhaust pipes, a rear wall having exhaust ports formed therein and a cover that encloses the interior space. Located within the enclosed space are muffler inserts secured to the floor and also to the front and rear walls. Each insert has a domed portion defining a muffling chamber that communicates with the respective exhaust pipe, and a second domed chamber defining an expansion chamber that communicates with the respective exhaust port located in the rear wall of the housing.

U.S. Pat No. 5,934,959, which issued to Inman et al. on Aug. 10, 1999, describes a marine muffler. It comprises a housing having an exhaust inlet and an exhaust outlet. A first exhaust chamber is disposed concentrically within the housing and is connected within the exhaust inlet. The first exhaust chamber includes as plurality of openings through a first exhaust chamber wall for distributing exhaust gas radially outwardly therethrough. A second exhaust chamber is disposed concentrically around the first exhaust chamber and receives exhaust gas passed to it from the first exhaust chamber.

U.S. Pat No. 5,980,343, which issued to Rolinski on Nov. 9, 1999, describes an exhaust system for marine vessels. A two pathway exhaust and water discharge through-hull system is coupled to a muffler for separating exhaust gases and cooling water at operating speeds such that at low engine speeds exhaust gases and water are discharged through a first outlet preferably above the water line and, when the engine speed is increased above a predetermined level, exhaust gases are discharged through a second outlet which communicates with a streamlined, low back pressure underwater discharge skeg and water is discharged through the first outlet.

U.S. Pat No. 6,244,918, which issued to Cameron on Jun. 12, 2001, describes a noise muffler exhaust filter for a marine engine. A muffler-filter apparatus comprises a filter housing providing a flexible cylindrical wall enclosed at one end by a screen integrally joined peripherally with a distal end rim of the cylindrical wall and a strap device for tightening a proximal end rim of the cylindrical wall for enabling the proximal end rim of the cylindrical wall to be fixed into a propeller hub of an outboard motor so as to position the filter housing for receiving exhaust of the outboard motor's engine.

U.S. Pat No. 6,800,005, which issued to Yokoya on Oct. 5, 2004, describes an exhaust system for a small watercraft. Exhaust gas can flow smoothly through the system and includes a water muffler in the exhaust system for an engine incorporated in a small watercraft. An exhaust pipe is connected to the water muffler extending upwardly once and then extending downwardly in such a manner so as to have a substantially U-shape. Spiral baffle plates are provided for spirally introducing exhaust gas on an inner face of the U-shape exhaust pipe. Since the baffle plates are placed on the exhaust pipe, cooling water and exhaust gas can be separated from each other.

U.S. Pat No. 6,820,419, which issued to Ford et al. on Nov. 23, 2004, describes a marine wet exhaust system. The system injects water into the exhaust flow for cooling and attenuating noise and includes a particulate capture and containment system for removing particulates and fluid contaminants from the exhaust gas and the waste cooling water of the discharge. With a first embodiment, this is accomplished by separating the waste cooling water and entrained particulates from the exhaust gas in a muffler/separator, accumulating the waste cooling water and entrained particulates in a reservoir, and separating the entrained particulates from the waste cooling water in a filter.

U.S. Pat No. 6,913,499, which issued to Matsuda on Jul. 5, 2005, describes an exhaust passage for a small watercraft. It is configured to discharge an exhaust gas from an engine of a small watercraft and comprises at least a first exhaust pipe, a second exhaust pipe connected to the first exhaust pipe, and a connecting structure configured to connect the first exhaust pipe and the second exhaust pipe to each other. The connecting structure includes a first tubular insertion end portion provided at a connecting end portion of the first exhaust pipe so as to protrude toward a connecting end portion of the second exhaust pipe.

U.S. Pat No. 7,156,710, which issued to Yokoya et al. on Jan. 2, 2007, describes an exhaust system for a small sized boat. It can efficiently reduce exhaust noises in a low frequency band and includes a water muffler provided at one location along exhaust pipes extending from an engine disposed in a boat body. The inside of the water muffler is divided into a single expansion chamber and a resonator chamber and a front exhaust pipe coupled to the engine and a rear exhaust pipe opened to the outside of the boat are connected to the expansion chamber. Between the front exhaust pipe opened to the inside of the expansion chamber and the rear exhaust pipe, a water controlling plate is provided in an upper side of the expansion chamber.

The patents described above are hereby expressly incorporated by reference in the description of the present invention.

SUMMARY OF THE INVENTION

A marine engine exhaust silencing system made in accordance with a preferred embodiment of the present invention comprises an engine disposed within a marine vessel, an exhaust conduit connected in fluid communication with a plurality of exhaust ports of the engine and a muffler attached to a rear surface of a transom of the marine vessel. The exhaust conduit extends through the transom of the marine vessel and the muffler is provided with first and second chambers configured to direct exhaust gas from the exhaust conduit through the first chamber and into the second chamber. The second chamber has an outlet which is configured to direct the exhaust gas away from the muffler in a direction which is both downward toward a surface of a body of water in which the marine vessel is operating and forward toward the transom.

In a preferred embodiment of the present invention, the plurality of exhaust ports of the engine comprises a first plurality of exhaust ports on a first side of the engine and a second plurality of exhaust ports on a second side of the engine. The first plurality of exhaust ports is connected to the exhaust conduit by a first exhaust pipe and the second plurality of exhaust ports is connected to the exhaust conduit by a second exhaust pipe. The outlet of the muffler comprises a surface which is configured to deflect the exhaust gas from a primarily forward direction toward the transom toward a downward direction toward the surface of the body of water in which the marine vessel is operating. The outlet of the muffler can also comprise a baffle plate which is configured to cause the exhaust gas to turn toward a generally forward direction toward the transom.

In a particularly preferred embodiment of the present invention, it further comprises an auxiliary exhaust passage connected in fluid communication with the exhaust conduit, an auxiliary muffler having an inlet connected in fluid communication with the auxiliary exhaust passage and an outlet extending through the transom, and a shroud attached to the rear surface of the transom and configured to direct a portion of the exhaust gas, which passes through the auxiliary muffler, in a generally downward direction toward the surface of the body of water in which the marine vessel is operating. In a particularly preferred embodiment of the present invention, it further comprises a drain opening formed in the muffler and configured to permit water to flow out of the muffler. The drain opening can be formed in a surface of the first chamber. A plurality of exhaust openings can be connected in fluid communication between the first and second chambers of the muffler.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more fully and completely understood from a reading of the description of the preferred embodiment in conjunction with the drawings, in which:

FIG. 1 is a partially sectioned view of a marine propulsion system incorporating a preferred embodiment of the present invention;

FIG. 2 is a view of a marine propulsion system viewed in a direction from within the marine vessel;

FIG. 3 illustrates the exhaust system in conjunction with an idle relief exhaust circuit; and

FIG. 4 is a rear view of a marine vessel showing the rear surface of the transom and the location of several components of a preferred embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Throughout the description of the preferred embodiment of the present invention, like components will be identified by like reference numerals.

FIG. 1 is a side section view of an engine exhaust silencing system made in accordance with a preferred embodiment of the present invention. It shows the muffler 10 attached to a rear surface 12 of a transom 14 of a marine vessel. It also shows an exhaust conduit 20 which directs a flow of exhaust gas from an engine 24, through the transom 14, and into the muffler 10.

FIG. 2 is an isometric view of the marine engine exhaust silencing system in a direction as seen from inside the marine vessel. It shows the Y-connection between the first and second exhaust pipes, 31 and 32, the engine 24, and the exhaust conduit 20.

FIG. 3 illustrates an embodiment of the present invention in which an auxiliary exhaust passage 40 is connected in fluid communication with the exhaust conduit 20 and with an auxiliary muffler 44.

FIG. 4 is a view from behind a marine vessel which illustrates the rear surface 12 of the transom 14, the muffler 10, a marine drive unit 50, and a shroud 54 which is used to cover an outlet of the auxiliary muffler 44 and direct the flow, which passes through the auxiliary muffler 44, in a downward direction toward the surface of the body of water in which the marine vessel is operating.

In the section view of FIG. 1, the muffler 10 is shown attached to the rear surface 12 of the transom 14. The muffler 10 has a first chamber 61 and a second chamber 62. The first and second chambers are configured to direct exhaust gas from the exhaust conduit 20 through the first chamber 61 and into the second chamber 62. The second chamber 62 has an outlet 66 which is configured to direct the exhaust gas away from the muffler 10 in a direction which is both downward toward a surface 70 of a body of water in which the marine vessel is operating and forward toward the transom 14. The resulting direction of the flow of exhaust gas is generally represented by arrow 74 in FIG. 1.

With continued reference to FIG. 1, the outlet 66 comprises a surface 80 which is configured to deflect the exhaust gas from a primarily forward direction, toward the transom, in a downward direction toward the surface 70 of the body of water in which the marine vessel is operating. The outlet 66 also comprises a baffle plate 82 which is configured to cause the exhaust gas to turn toward a generally forward direction toward the transom 14. The turning of the exhaust gas stream is the result of the effects created by baffle plate 82 and the bottom inside surface 67 identified in FIG. 1. These surfaces, in combination with each other, turn the flow of exhaust gas from a generally downward direction to a forward direction. With respect to the directions of flow of exhaust gas, as described above, it should be understood that in FIG. 1 the forward direction is toward the left because the exhaust gas flowing from the outlet 66 toward the transom 14 flows in a forward direction relative to the general movement of the marine vessel. The downward direction, toward the surface 70 of the body of water, is generally downward in FIG. 1. As a result of the deflection surface 80 and the baffle plate 82, the exhaust gas flows in the direction represented by arrow 74 which is generally downward and in a forward direction toward the transom 14. It has been determined that this flow of exhaust gas as it leaves the muffler 10 is particularly advantageous with regard to reducing the noise emanating from the exhaust system.

With continued reference to FIG. 1, a particularly preferred embodiment of the present invention further comprises a drain opening 90 formed in the muffler 10 proximate the transom and configured to permit water to flow out of the muffler. The drain opening, in a particularly preferred embodiment of the present invention, is formed in a surface 92 of the first chamber 61. In the preferred embodiment of the present invention illustrated in FIG. 1, a plurality of exhaust openings, 94-96, are connected in fluid communication between the first and second chambers, 61 and 62. The exhaust gas flows from the engine 24 (as represented by the dashed line arrow), through the exhaust conduit 20, and into the first chamber 61 of the muffler 10. Water, flowing with the exhaust gas, is separated from the exhaust gas flow and is allowed to flow through the drain opening 90 to evacuate the first chamber 61. In doing so, the evacuation of the water maximizes the usable volume of the first chamber 61 for the purpose of reducing the sound levels emanating from the outlet 66. The exhaust gas continues to flow through the plurality of exhaust openings, 94-96, and into the second chamber 62. The baffle plate 82 turns the flow of exhaust gas toward a forward direction (toward the left in FIG. 1 and generally toward the transom 14) in cooperation with surface 67 as described above. As the exhaust gas continues to flow out of the outlet 66, the deflection surface 80 turns the flow of exhaust gas from a forward direction, as a result of the baffle plate 82, toward a downward direction toward the surface 70 of the body of water in which the marine vessel is operating. This results in a downward and forward direction of flow of the exhaust gas which, as a result, reduces the sound level emanating from the outlet 66 region of the system.

With continued reference to FIGS. 1-4, the provision of a Y-type connection between the first and second exhaust pipes, 31 and 32, induces the exhaust gas to flow through an exhaust conduit 20 which has the cross-sectional area which is generally equivalent to either of the first and second exhaust pipes, 31 and 32. This reduces the overall cross-sectional area from which noise can be emitted, in comparison to the alternative configuration in which both exhaust pipes individually pass through the transom 14.

With continued reference to FIGS. 1-4, the plurality of exhaust ports of the engine, in a preferred embodiment of the present invention, comprises a first plurality of exhaust ports, 101-104, on a first side 106 of the engine 24 and a second plurality of exhaust ports, 111-114, on a second side 116 of the engine. The exhaust ports 111-114 are not visible in FIG. 2, but are generally identical and symmetrical with exhaust ports 101-104 which are visible. The first plurality of exhaust ports, 101-104, is connected to the exhaust conduit 20 by the first exhaust pipe 31 and the second plurality of exhaust ports, 111-114, is connected to the exhaust conduit 20 by the second exhaust pipe 32.

The primary intended function of the present invention is to reduce the sound level of noise emanating from the marine propulsion system of a marine vessel. Various regulations are directed to limiting the allowable noise level from marine engines. As an example, in the European Union, it is currently required that a pass-by sound level not exceed 78 db for a twin engine boat as tested by a particular set of international standards. This sound level requirement is very difficult, if not impossible, to achieve with available marine mufflers and standard outlet exhaust tail pipes. Typical high performance sports boats in the 30 to 40 foot size range use two V-8 engines. The four tailpipes, which are typical in arrangements of this type, sterndrive units, steering hardware, trim tab hardware, and associated support rigging make available very little transom space that would allow additional mufflers to be used. In addition, the mufflers used in these applications must be able to also pass the amount of cooling water that is mixed with the exhaust gas in applications of these types. As a result, it is very difficult to meet the required noise reduction limits while maintaining reasonable exhaust back pressure magnitudes. The present invention achieves the desired goals through the combination of various advantageous design configurations. As an example, by combining two exhaust pipes, 31 and 32, each one before extending the exhaust conduit 20 through the transom 14, only a single muffler 10 is required for each engine of the marine vessel. This single outlet of the exhaust conduit 20 is approximately half the combined area of the two exhaust pipes, 31 and 32. This helps to reduce the noise emanating from the system. The muffler 10, as described above, is a separate component from the exhaust conduit 20 and covers the outlet opening of the exhaust conduit 20. It uses the transom 14 as the inlet chamber wall for the first chamber 61. The outlet 66 of the muffler 10 directs the exhaust gas s both downwardly and forwardly toward the transom 14. Most known mufflers cause the exhaust gas to exit in a direction away from the transom 14. The drain opening 90 assists in evacuating water from the first chamber 61 in order to minimize back pressure and maximize the available volume within the first chamber 61 for use in silencing the noise emanating from the exhaust system. In a particularly preferred embodiment of the present invention, the outlet 66 is positioned to be underwater when the boat is operating at speeds less than planing speed. This further reduces noise.

With continued reference to FIGS. 1-4, an idle relief system, or vacuum break, is provided by connecting an auxiliary exhaust passage 40 in fluid communication with the exhaust conduit 20 and also by connecting the auxiliary muffler 44 between the auxiliary exhaust passage 40 and a location on the rear side of the transom 14. This auxiliary system provides an idle relief path for the exhaust when the marine vessel is not operating at speeds above its planing speed. The conduits of the auxiliary system are routed from the exhaust conduit 20 to a location behind the transom 14 and above the water line. Noise emanating from the outlet of the auxiliary muffler 44 is reduced by the shroud 54 that directs the exhaust downwardly and toward the surface 70 of water.

With continued reference to FIGS. 1-4, it can be seen that the combination of several advantageous design characteristics significantly reduce the noise emanating from the exhaust system of the marine vessel. These design characteristics include the use of the Y-shaped exhaust configuration in which two exhaust pipes, 31 and 32, are joined to provide a single passage which is generally the same cross-sectional area as either one of the two exhaust pipes, 31 and 32. The muffler 12 provides two chambers, 61 and 62, and a drain opening 90 that facilitates the draining of water from the first chamber 61 so that the usable volume of the first chamber can remain at its maximum capacity for the purpose of reducing noise levels emanating from the muffler 10. At the outlet 66 of the muffler 10, the baffle plate 82 advantageously turns the exhaust gas stream in a direction toward the transom 14 rather than allow the exhaust gas to exit from the muffler 10 in a direction toward the rear and away from the marine vessel. The use of a deflection surface 80 causes the exhaust gas stream 74 to move in a downward direction. The forward and downward direction of the exhaust gas is significantly beneficial in reducing the noise level emanating toward directions above and to the rear of the marine vessel. Instead, the noise is directed, along with the exhaust gas, toward the surface 70 of the body of water which further attenuates its magnitude. The present invention permits the sound to be significantly attenuated through the use of a single muffler 10 for each engine of the marine vessel. It has been found that the use of two chambers, 61 and 62, in conjunction with three exhaust openings, 94-96, between the chambers is particularly advantageous. However, it should be understood that alternative numbers of chambers and exhaust openings between the chambers are also within the scope of the present invention.

Although the present invention has been described with particular specificity and illustrated to show a preferred embodiment, it should be understood that alternative embodiments are also within its scope. 

1. A marine engine exhaust silencing system, comprising: an engine disposed within a marine vessel; an exhaust conduit connected in fluid communication with a plurality of exhaust ports of said engine and extending through a transom of said marine vessel; a muffler attached to a rear surface of said transom, said muffler having first and second chambers configured to direct exhaust gas from said exhaust conduit through said first chamber and into said second chamber, said second chamber having an outlet which is configured to direct said exhaust gas away from said muffler in a direction which is both downward toward a surface of a body of water in which said marine vessel is operating and forward toward said transom; wherein: said outlet comprises a plate which is configured to cause said exhaust gas to turn toward a generally forward direction toward said transom; said outlet further comprises a surface which is configured to deflect said exhaust gas received from said plate from a primarily forward direction toward said transom toward a downward direction toward said surface of said body of water in which said marine vessel is operating.
 2. The silencing system of claim 1, wherein: said plurality of exhaust ports of said engine comprises a first plurality of exhaust ports on a first side of said engine and a second plurality of exhaust ports on a second side of said engine, said first plurality of exhaust ports being connected to said exhaust conduit by a first exhaust pipe, said second plurality of exhaust ports being connected to said exhaust conduit by a second exhaust pipe. 3-4. (canceled)
 5. The silencing system of claim 1, further comprising: an auxiliary exhaust passage connected in fluid communication with said exhaust conduit; an auxiliary muffler having an inlet connected in fluid communication with said auxiliary exhaust passage and an outlet extending through said transom; and a shroud attached to said rear surface of said transom and configured to direct a portion of said exhaust gas, which passes through said auxiliary muffler, in a generally downward direction toward said surface of said body of water in which said marine vessel is operating.
 6. The silencing system of claim 1, further comprising: a drain opening formed in said muffler and configured to permit water to flow out of said muffler.
 7. The silencing system of claim 6, wherein: said drain opening is formed in a surface of said first chamber. 8-20. (canceled) 